Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$194.49	6.288%	$206.7195	$206.72	$206.70	$206.70
Purchase #2	$89.39	11.817%	$99.9532	$99.95	$99.95	$100.00
Purchase #3	$179.54	6.701%	$191.571	$191.57	$191.55	$191.60
Purchase #4	$210.43	12.192%	$236.0856	$236.09	$236.10	$236.10
Purchase #5	$54.68	9.553%	$59.9036	$59.90	$59.90	$59.90
Purchase #6	$19.84	13.194%	$22.4577	$22.46	$22.45	$22.50
Purchase #7	$191.47	3.686%	$198.5276	$198.53	$198.55	$198.50
7 purchase totals =	$939.84		$1,015.2182	$1,015.22	$1,015.20	$1,015.30